<template>
  <div class="rbt-pagination">
    <a v-if="myCurrentPage <= 1" href="javascript:;" class="disabled">上一页</a>
    <a v-else href="javascript:;" @click="changePage(myCurrentPage - 1)"
      >上一页</a
    >
    <span v-if="pager.start > 1">...</span>
    <a
      v-for="i in pager.btnArr"
      :key="i"
      href="javascript:;"
      :class="{ active: i === myCurrentPage }"
      @click="changePage(i)"
      >{{ i }}</a
    >
    <span v-if="pager.end < pager.pageCount">...</span>
    <a
      v-if="myCurrentPage >= pager.pageCount"
      href="javascript:;"
      class="disabled"
      >下一页</a
    >
    <a v-else href="javascript:;" @click="changePage(myCurrentPage - 1)"
      >下一页</a
    >
  </div>
</template>

<script setup lang="ts">
const props = defineProps({
  total: {
    type: Number,
    default: 100
  },
  currentPage: {
    type: Number,
    default: 1
  },
  pageSize: {
    type: Number,
    default: 10
  }
})

const emits = defineEmits<{
  (e: 'current-change', value: number): void
}>()
// 总条数
const myTotal = ref(100)
// 每页条数
const myPageSize = ref(10)
// 当前第几页
const myCurrentPage = ref(1)
// 按钮个数
const btnCount = 5

// 监听传入的值变化
watch(
  props,
  () => {
    myTotal.value = props.total
    myPageSize.value = props.pageSize
    myCurrentPage.value = props.currentPage
  },
  { immediate: true }
)

// 重点: 根据上述数据得到 (总页数 起始页码 结束页码 按钮数组)
const pager = computed(() => {
  // 计算总页数
  const pageCount = Math.ceil(myTotal.value / myPageSize.value)
  // 计算起始页码和结束页码
  // 1. 理想情况根据当前页码 和按钮个数可得到
  let start = myCurrentPage.value - Math.floor(btnCount / 2)
  let end = start + btnCount - 1
  // 2.1如果起始页码小于1 需要重新计算
  if (start < 1) {
    start = 1
    end = start + btnCount - 1 > pageCount ? pageCount : start + btnCount - 1
  }

  // 2.2 如果结束页码大于总页数 需要重新计算
  if (end > pageCount) {
    end = pageCount
    start = end - btnCount + 1 < 1 ? 1 : end - btnCount + 1
  }

  // 处理完毕start和end得到按钮数组
  const btnArr = []
  for (let i = start; i <= end; i++) {
    btnArr.push(i)
  }
  return { pageCount, start, end, btnArr }
})

// 改变页码
const changePage = (newPage: number) => {
  if (myCurrentPage.value !== newPage) {
    myCurrentPage.value = newPage
    emits('current-change', newPage)
  }
}
</script>

<style scoped lang="scss">
.rbt-pagination {
  display: flex;
  justify-content: center;
  padding: 30px;
  > a {
    display: inline-block;
    padding: 5px 10px;
    border: 1px solid #e4e4e4;
    border-radius: 4px;
    margin-right: 10px;
    &:hover {
      color: $rbtColor;
    }
    &.active {
      background: $rbtColor;
      color: #fff;
      border-color: $rbtColor;
    }
    &.disabled {
      cursor: not-allowed;
      opacity: 0.4;
      &:hover {
        color: #333;
      }
    }
  }
  > span {
    margin-right: 10px;
  }
}
</style>
